Influence of Experimental Conditions on the Catalyst Degradation in the Durability Test

Accelerated durability tests (ADTs) were carried out for a carbon-supported platinum catalyst using a rotating disk electrode at various rotation rates for various catalyst loadings. The electrochemical surface area (ECSA) of platinum, TEM-observed relative particle size distribution, and Pt ion concentration in the electrolyte were analyzed. Their results were combined to provide the absolute change in the particle size distribution. The loss of the normalized ECSA increased with increasing the rotation rate and/or decreasing the catalyst loading. The detailed analysis showed that the reciprocal of the normalized ECSA loss rate linearly increased with the increases in ω −1/2 (ω: angular frequency of rotation) and the catalyst loading; these results suggests that ECSA loss in ADTs is significantly affected by Pt ion diffusion in the electrolyte. By extrapolating these linear relations to zero, the ECSA loss rate at the hypothetical conditions, in which all the dissolved platinum ions would flow out to the electrolyte without re-deposition, was obtained.